Electrodynamic machine



12, 1949 C, M HULBERT 294759837 ELECTRODYNAMIC MACHINE Filed March 5, 1946 4 Sheets-Sheet 2 e/ '"4 JW 7 *MII W d (D @il Juy l2, i949. (C, g-i, HULEERT 475,837

ELECTRODYNAMIC MACHINE Filed March s, 1946 4 sheets-sheet s u) la Patented July 12, 1949 UNITED STATES PATENT OFFICE ELECTRQDYNAMIC MACHINE Clinton H. Hulbert, Long Beach, Calif.

Application March 5, 1946, Serial No. 652,177

22 Claims. 1

My invention relates in general to electrodynamic machines, and a primary object of the invention is to provide a machine oi this general character having a novel and improved commutator structure which renders the machine capable of performing a wide variety of functions.

An important object of my invention is the provision of an electrodynamic machine which is capable of generating electrical components having a Wide variety of Wave forms ranging from sinusoidal and flat-top waves to intermittent pulsations.

Another important object of my invention is to provide an electrodynamic machine of this character which is capable of generating either direct current or alternating current.

A further object is to provide an electrodynamic machine which is capable of operating as an alternator to generate alternating current in the larmature circuit thereof, and Which is capable of operating as an induction generator to generate direct current and alternating current, either individually or simultaneously. A related object is to provide an electrodynamic machine which is capable of operating as an induction generator to generate alternating current in the field circuit thereof, and/or direct current in the armature circuit. When operating as an induction generator, the output of the machine may be either direct current or alternating current, or both simultaneously, which is still another object of my invention.

The foregoing objects of my invention, together with various other objects and various advantages Which will be apparent hereinafter, may be realized by means of the exemplary embodiments of my invention which are illustrated in the accompanying drawings and which are described in detail hereinafter. Referring to the drawings, which are for illustrative purposes only:

Fig. 1 is a partially schematic View illustrating an electrodynamic machine which embodies the fundamental principles oi my invention;

Fig. 2 is a diagrammatic view in the form of a flat development which illustrates the armature Winding and the commutator structure of the embodiment shown in Fig. 1;

Fig. 3 is a simplied diagrammatic View illus- `trating a brush circuit which may be employed in 2 connection with the embodiment of Figs. 1 and 2 when the machine is operating as an alternator;

Fig. 4 is a View illustrating the Wave forms and phase relationships of electrical components derived from the brush circuit shown in Fig. 3;

Fig. 5 is a diagrammatic View which is similar to Fig. 3 and which illustrates another brush circuit for use in connection with the embodiment of Figs. l and 2;

Figs. 6 and 7 are Views illustrating the Wave forms and phase relationships of electrical components derived from the brush circuit shown in Fig. 5;

Fig. 8 is a diagrammatic View which is similar to Figs. 3 and 5 and which illustrates still another brush circuit;

Figs. 9 and l0 are views illustrating the wave forms and phase relationships derived from the brush circuit shown in Fig. 8;

Figs. l1 and 12 are diagrammatic views illustrating circuits for generating various electrical components in connection with the embodiment shown in Figs. 1 and 2;

Figs. 13 and 14 are diagrammatic views illustrating brush circuits which may be employed in connection with the embodiment shown in Figs. l and 2 when the machine is operating as an induction generator;

Figs. 15 and 16 are views illustrating the Wave forms of electrical components derived from the brush circuits shown in Figs. 13 and 14, respectively;

Figs. 17 and 18 are diagrammatic views illustrating other brush circuits which may be employed when the embodiment of Figs. l and 2 is operating as an induction generator;

Figs. 19 to 23 are diagrammatic views illustrating still other brush circuits which may be employed when the embodiment of Figs. l `and 2 is operating as an induction generator;

Figs. 24 to 26 are views illustrating the operation of the machine with the circuits illustrated in Figs. 19 to 21, respectively;

Figs. 27 and 29 are diagrammatic views which are similar to Fig. 2 and which illustrate additional embodiments of my invention; and

Figs. 28 and 30 are views illustrating the Wave forms of electrical components which may be generated by the embodiments shown in Figs. 27 and 29. respectively.

Referring particularly to Figs, 1 and 2, the embodiment illustrated therein includes a stator 50 which is provided with four pole pieces 5|, 52, 53, and 59 of laminated construction in the particular construction illustrated, although any desired number of pole pieces may be employed. The pole pieces 5I, 52, 53, and 54 are provided with field windings 55, 50, 51, and 58 thereon respectively, which are connected in series in the particular construction illustrated, the eld windings being so arranged that they are adapted to provide alternate north and south poles as indicated by the letters N, S, N and S on the pole pieces 5|, 52, 53, and 54, respectively, when the field windings are excited by direct current. The direct current may be supplied to the eld windings 55, 55, 51, and 58 through lines 59 and 60 which are connected to a source of direct current such as a battery 6|, a switch 62 and resistance 63 being provided in the line 60.

A rotor or armature 65 of laminated construction is mounted in the stator 50 in the conventional manner by means of a shaft and bearings which have been-omitted to preserve the clarity of the drawings, the rotor being provided withva plurality of slots 66 ytherein to receive the conductors of an armature winding 61. As best shown in Fig. 2, the armature winding' is a standard wave winding in the particular construction illustrated, the winding including a plurality of terminals which are indicated consecuti'vely by the numerals 1| to 93, inclusive. The 'characteristic form of the coils of the wavetype armature winding 61 as indicated by the heavy'line 95 in Fig. 2, the terminal 1| being connected to the terminal 82 which is in turn connected to the Aterminal 93 as indicated by the arrows on the heavy line 95. From the terminal 93', the winding 81 leads to the terminals 8|, 92, 9|,' 19, 99,*etc., until the winding returnsf'to the terminal 1| as is the conventional practice'in wave windings.

The stator 58 and rotor 65 are wound to correspond to the voltage and amperage required, and are wound so that each can function `inductively vand. independently of each other as will bev discussed in detail hereinafter, Although the armature winding 81 illustrated is a standard wave winding, any other suitable winding, such as a lap or drum winding, may be employed if desired. The armature winding 61 is preferably aI winding having equalized connections of all the terminals thereof which have the same rel-ative potential position, as indicated'by the interconnected terminals 1I, 82, and 93, in order to increase the winding efliciency in accordance with the conventional practice in armaturewindings wherein the output is taken from' only two br-ushes.

A'commutator 96 is carried by the rotor 85 and is rigidly secured thereto in any suitable manner, the manner in which the commutator is secured to the rotor not being shown specifically in' the drawings so that the essential features of 'the commutator structure vmay be illustrated more clearly. As best shownin Fig. 2, the commutator 98 includes a plurality of commutator segments which are circumferentially 'arranged and which are insulatedfrom each other in-a manner well knownin the art. The commutator segments are arrangedv in four groups which areindicated by the numerals 91, 98, 99, and |00, each-group of segments subtending an angle of 90 degrees, as indicated in Fig. 2, so that the groups 9-1 and 99 are spaced 180 degrees apart, andthe groups 98 the clarity of the drawings.

and |00 are also spaced 180 degrees apart, the groups 91 and 99 being spaced 90 degrees from the groups 98 and |00. The groups 91 and 99 are symmetrical with respect to each other, and the groups 98 and |08 are also symmetrical with respect to each other, as best shown in Fig. 1.

The group 91 includes a plurality of short segments lill, |02, |03, |04, |05, and |06 which are electrically connected to the terminals 1|, 12, 13, 14, 15 and 16, respectively, of the armature winding 81 as best shown in Fig. 2, no identifying numerals having been assigned to the conductors which connect the segments to the winding terminals for the purpose of preserving The group 98 includes a single long segment |050. which may be connected to the segment |96 of the group 91. The group 99 includes a plurality of short segments |01, |08, |09, H0, III, and H2 which are connected to the winding terminals 11, 18, 19, 09, 8l, and 82, respectively, and the group |00 includes a single long segment ||2a which may be connected to the segment ||2 of the group 99 the remaining winding. terminals, 83 to 93 inclusive, being unconnected.

In the particular construction illustrated, the machine includes four brushes ||5, H6, ||1,and I I8 which are spaced 90 degrees apart, and which engage the commutator 96. Although I have shown four brushes spaced l degrees apart, any desired number `of brushes and any spacing may be employed depending on the results desired, as will be described in detail hereinafter. As best shown in Fig. 1, the brushes H5, |5,. ||1, and M8 are connected to conductors ||9, |20, |2I, and E22, respectively, the brushes l5 and i1 being connected to a load |25 by theconductors ||9`and |2|'. rhe brush circuit defined bythe brushes I|5 and H1,` the conductors ||9 and |2|,y andthe load |25 is intended as illustrative only since a wide variety of brush circuits may be employed as will be discussed in detail hereinafter.

For convenience in illustrating and describing the embodiment of my invention which is shown in Figs. 1 and 2, the number of terminals of the armature winding 61., and the-number of com- ,mutator segments in the groups 91 and 99 are less'than the numbers thereof which are desirable in actual practice. In order to providlel greater efficiency and smoother operation, and in order to decrease any -commutator ripple, the number of winding terminals and commutator segments employed in actual practice should be greater than the number shown in the drawings as will be appreciated by those skilled in the art.

In general, my electrodynamicfmachine may be operated either as an alternator, or Aas an induction generator. When operating as an alternator, the eld `windings 55 to 58 are excited by direct current so that alternating current is generated at the brushes ||5 to H8. When operating as an induction generator., asmall current introduced into the armature winding 61 through the brushes ||5 to I|8 will cause the machine to generate alternating current in the iield circuit and direct current at .the brushes. In addition to the foregoing general methods of operating the machine, many variationsare also possible, The foregoing general methods of operating the machine 'will be described in detail hereinafter.

In order to understand the operation of my electrodynamic machine, it is necessary that the operation of its commutator structure be thoroughly"un'derstood. The operation of the commutator structure vmay'best be understood in connection with a description of the operation of the machine when operating as an alternator,

Considering the general case wherein the machine operates as an alternator, the field windings 55 to 58 may be excited by direct current from a source such as the battery 8| by closing the switch t2, thereby producing the alternate north and south poles 5I to 54 as previously described. Reierring particularly to Fig. 2 and considering the voltage between the brushes I I6 `and IH, which are spaced 90 degrees apart, it will be noted that the coils or the armature winding *5l which are connected to the brushes II B and II'i are adjacent each other so that the only vol*- age between these brushes is equal to the voltage between a pair of adjacent coils, which is very small. The brushes Ilil and II'I `are short circuited by the long commutator segment Iubo. so that this small voltage between two adjacent coils is dissipated as in the case of a conventional direct current generator, the net voltage between the ybrushes I i5 and I I'I being Zero when the armature tll is in the position shown in Fig. 2 with respect to the brushes. As the armature 55 is rotated by any suitable driving means (not shown) so that the commutator 96 moves from right to left as viewed in Fig. 2 (in the direction indicated by the arrow |30), the brush IIS ren mains in contact with the long commutator segment leila for one-quarter of a revolution (90 degrees) of the armature. Meanwhile, the brush lI'l successively engages the short commutator segments Illl to H2, inclusive, until at the end of one-quarter of a revolution of the armature d5, the entire space between the brushes IIl and i Il is filled with active coils `of the `armature winding lil' and the voltage therebetween is a maximum.

As the armature t5 is rotated further, the brush Ill engages the long conductor segment lIZa, and remains in engagement therewith until the armature has been rotated through one-half of a revolution (180 degrees). Meanwhile, the brush IIS successively engages the short commutator segments lill to I I2, inclusive, so that the number of active coils between the brushes H6 and II? is gradually decreased until these brushes are short circuited by the long commutator segment lIZa after one-half of a revolution of the armature @55 so that the Voltage between the brushes I IE and I I'l is again Zero.

It will be apparent that the voltage between the brushes i lli `and I I T will be a maximum when the armature 65 is in the 90 degree position, i. e., when the armature has rotated through onequarter of a revolution from the position shown in Fig. 2, since the space between these brushes is then lled with the maximum number of coils of the winding el. When the armature 65 is in the 90 degree position, the brushes I I6 and II'I are in full commutation, vthe same voltage being generated as would be the case with a conventional wave-wound four pole generator.

Considering `the armature position shown in Fig. 2 as the zero degree position, the Voltage between `the brushes il@ and II'I thus increases from zero at the zero degree position to a maximum at the 90 degree position, and then decreases to zero again after 180 degrees of rotation. As the armature 65 is rotated beyond 180 degrees, the brush II'I successively engages the short commutator segments II, H32, H13, etc., while the brush II'S remains in contact with the' long segment I I2a so that after 270 degrees of rotation of the armature, the voltage between the brushes I IIB and II'I is again va maximum. Similarly, after 360 degrees of rotation of the armature 65, the voltage between the brushes I I6 and lll is again zero.

However, #after 270 degrees of rotation of the armature 65, the magnetic eld in which the active coils between the brushes IIB land II`I are disposed is opposite to the magnetic eld in which the active coils between these brushes were disposed after only degrees of rotation of the armature. Consequently, the voltages between the brushes llt and III after 9G and 270 degrees of rotation will be of equal magnitudes but of opposite signs, the voltage in one of these positions being positive, and being negative in the other.

Thus, an alternating voltage is generated between the brushes EI'S and II'I, [the frequency thereof being one cycle per revolution of the armature t 'will be apparent that the voltage generated between the brushes I I 'I 'and I I 8, which lag behind the brushes I I6 and I II by 90 degrees, will be identical to that generated between the brushes iIG and ill', except that it will lag by one-quarter or" a cycle, Aor 90 degrees. Similarly, the voltages between the brushes I I8 and I I5 and between the brushes I l5 and I I6 will also be identical, but will lag by degrees and 270 degrees, respectively.

Iihus, the iour pairs of brushes which are spaced 90 degrees apart, the brushes IIB and III, illI and H8, llt and IIE, and II5 and IIB, produce four phases of alternating current, each phase lagging the preceding phase by 90 degrees. The next -step in describing the operation of the ccmmutator structure of my electrodynamic machine is to determine the nature of the wave form of the voltage generated between any pair of adjacent brushes, which is the subject of the following paragraphs.

lin order to arrive at a mathematical expression for the Voltage generated between any pair of adjacent brushes, it shall be assumed that the number of commutator segments compri-sing the groups 9i' and 99 is very large to provide a smooth curve. It shall also be assumed that a coil of the winding S'i' which moves past the field poles el to at a uniform speed has a voltage generated therein which is of pure sine wave form.

The armature position shown in Fig. 2 with respect to the brushes H5 to II8 shall be considered the starting position, for which Q=0, wherein Q is the angle through which the armature has rotated in the direction of the arrow Any conductor of the winding S'I which is disposed midway between adjacent of the poles 5i to lidi is disposed in a magnetic field of zero strength so that the voltage generated in the conductor is zero, such a conductor being indicated by the numeral I3I in Fig. 2 which, a1- though not precisely midway between the poles 57i and 52, may be considered as being midway therebetween for the purposes of this analysis. Thus, when 62:0, the voltage generated in the conductor Il is zero, and when Q=45 degrees, this conductor will be disposed opposite the center of the north pole 5I where the magnetic eld strength is a maximum so that the Voltage generated therein is a maximum. When Q=90 degrees, the voltage generated in the conductor i3d will again be zero, etc.

1r H=the maximum magnetic field strength, then it will be apparent that the field strength at any position, which shall be indicated by the Yletter h, will be:

As previously discussed, as the armature 65 rotates beyond the starting point where (2:0, active coils of the Winding 61 `gradually move into the space between the brushes ||6 and H1, and

the brush |l'1 successively engages the commutator segments |01, |08, etc. However, as the brush IIT begins to engage the segment |01, the conductors of the coil which is connected to the segment |01 are in a zero eld and gradually move into a eld of increasing strength as the armature 65 rotates. As the armature 65 continues to rotate, the brush H1 successively engages the segments |08, |09, etc., and the coil which is connected to the segment |01 continues to move into a stronger and stronger field as the space between this coil and its original position becomes filled with the coils which are connected to the segments |08, |09, etc., the latter coils also moving into a eld of increasing strength.

Now, if w is equal to the angular velocity of the armature 65, and t is equal to the time elapsed since the armature was at the starting positionwhere (2:0,

ont (14:2)

Atan arma-ture position where Q:Q1, the voltage generated between the brushes |16 and ||1 isfequal to the `sum of the voltages generated in the. conductors of the coils disposed between the positions Q:Q1 and Q:0. The sum of these voltages vmay be found by solving a simple'differential equation. Letting E equal the maximum voltage generated between the brushes |16 and lll, and letting e equal the voltage therebetween at any time t, the instantaneous voltage when Q:Q1 will be e:e1. As they armature 65 rotates a small additional amount beyond the position where Q:Q1 to a position where .Q:Q2, then e:e2. The change in e between 6:61 and c:e2 i-s due to the addition of conductors of the coils of the winding 61 as the armature 65 moves from Q=Q1 to Q:Q2. Letting the change in e be equalto de, which is proportional to the change in the magnetic eld strength h as the armature 65 moves from Q:Q1 to Q:Q2, and letting Q2-Q1:dQ, then de:Kh

where h:the field strength at Q=Q2 K:the field strength gradient.

In Equation 143,;the term Kh represents the number of `lines of force cut in a given unit of time t, so that K is not strictly a constant. Letting L equalthe length of the conductors of the coils o1 the winding 6i, the number of lines of force in the space between Q=Q1 and Q:Q2 is LhdQ. If the number of conductors in a unit angle Q of the armature 65 is equal to C, then CdQ conductors are in the space dQ. However, in order that all of the conductors in the space dQwill cutl all of the lines of force in the space aZQ, it will be apparent that the armature 65 must rotate through an angle ZdQ. Consequently, the voltage generated in the conductors in the space (EQ as the armature 65 rotates through the angle dQ is equal to one-half the voltage which' would be generated if all of the conductors in the space dQ cut all 'of the lines of force therein. Letting the actual number of lines of force cut by the conductors in the space dQ as the armature v|55 rotate-s through the angle dQ be equalto N, then and S From vEquation 142, the Vtime dt requiredY to cut the lines -of .viorcein the spacefdQ as the armature rotates through the vangledQ is equal to dQ/w,so that the number of lines of force cutper unit time t is N/t, or Nw/dQor Substituting the value of h Ifound in Equation 141, then N/t:HCLw sin 2QdQ/2 (14:6)

|| aspreviously stated. Thus, substituting this value for E in Equation 146,

de=EiSin 26261@ (147) Since sin 2Q:2 sin vQcos Q, and substituting this value ior sin 2Q in Equation'lirl',

de:2E sin Q cos QdQ f (148) Integrating Equation 148,

e:E sin2 Q-l-C (149) Solving for C in Equation 149, since when Q:O, 9:0, consequently 0:0.

Thus, the equation for thewave formof the voltage generated betweenthe brushesil'and l i1 is,

Equation 150y holds forV thefirstralSO'degreesof rotation of the armature 55, ire., from 62:0 to 62:180degrees, and since the magneticneld is reversed-'from 180 degrees to-SGO degrees oi. armature rotation, as -discussed previously, the `equation for the wave form ofl the-voltage betweei the brushes II-G :and ll for Q:180 degrees to (2:36() degrees' is,

As previously mentioned, the .voltagesgenerated betweeirthefbrushes and I |8,. H8 "and H5, andl I5 and H6 are identical tothe voltage generated betweenthe brushes'l I6 and l1 except that they lag by 90 degrees, 180 degrees, and 270 degrees, respectively. The wave forms and phase relationships of these voltages arey shown in Fig. 4, the brush connections being, :indicated in the simplified schematic diagram of Fig. 3. Thus, the voltage phase generated between the brushes H5 and Ht is indicated by the solid curve |55 in Fig. fi, the voltage phase'between thebrushes H6 and |11 by the dotted curve |56, the phase between the brushes andy |8 by the dashed curve |51, and the phase between the brushes l I8 andv H5 by the dot-dash curve |58, the brush conneetionsior thevoltage phases 65,1156; |51, and(y |58 beingindicated Adiagrammatically ,by the dimensional arrows-H9, |60, |5|, and E62, respectively, in Fig. 3.

Considering otheiww'ave formsv obtainable with my electro'dynamic machine, and'reierringl particularly to Fig. 5, a'pair ofi brushes-Which are spacedl'degrees apart may be connectedv to produce @flat-topwaveform. Foriexamplel if the brushes |I and are connected as indicated by the dimensional arrow |55, the resulting wave form will be the algebraic sum of the curves |55 and |56 of Fig. 4. The curves |55 and |56 are also shown in Fig. 6, and the alge-- braic sum thereof is the dotted curve |66. The curve |66 is a fiat-top wave wherein the voltage changes from a maximum negative value to a maximum positive value in 9() degrees of rotation of the armature 65, remains constant at the maximum positive value for the next 90 degrees of rotation, reverses from the maximum positive value to the maximum negative value in the iollowing 90 degrees of rotation, and remains constant at the maximum negative value for the next 90 degrees.

The fact that the curve |65 is fiat from 9() to 180y degrees of armature rotation may be shown by considering the equation thereof in this range. From 90 to 180 degrees rotation, the equation of the curve |55 is Equation 150, i. e.,

e=E sin2 Q (150) The equation of the curve |56 in this range is,

e=E sin2(Q-90) (167) since the curve |56 lags the curve |55 by 90 degrees. Since sin2(Q-90) =cos2Q, the equation of curve |56 between 90 and 180 degrees of armature rotation is,

E=e cos2Q (168) Consequently, the equation for the curve |66 in this range, letting the voltage of the curve |65 be e166, is,

e1se=E(sin2 Q-l-cos2 Q) (169) e1es=E (170) Similarly, it may be shown that the voltage represent-ed by the curve |66 from 270 to 360 degrees of armature rotation is equal to -E.

Referring again to Fig. 5, if the brushes i3 and H6, which are spaced 180 degrees apart, are also connected as indicated by the dimensional arrow |'i|, a second nat-top wave |12 may be derived which lags the rst fiat-top wave |65 by 90 degrees as shown in Fig. 7.

The preceding description of the operation of the commutator structure in connection with the operation of my electrodynamic machine as an alternator is based on the relative positions of the brushes ||5 to I8 and the poles 5| to 54 which are shown in Fig. 2, or when the brushes are in full commutation. Now consider the brushes ||5 and |18 in positions such that the brushes are, in effect, displaced forwardly in the direction of movement of the armature 65 by an angle R with respect to the poles 5| to 55|, the brushes being displaced in the direction of the arrow |36, i. e., being located to the left of their positions as shown in Fig. 2. This arrangement is shown schematically in the simlplied diagram of Fig. 8.

Assuming that the armature 65 has been rotated through an angle R for convenience so that the relative positions of the brushes H5 to 8 and the commutator 95 are as shown in Fig. 2, the angle through which the armature 65 rotates Afrom. this new position will be taken as Q. Following the same procedure as employed previously, the voltage increment between any pair of adjacent brushes, such as the brushes H6 and Si?, for example, as the armature 65 rotates through an angle dQ is,

10 de=E sin 2 o+m (173) the angle (Q-l-R) being the angle through which the armature 65 has rotated from the position shown in Fig, 2 relative to the poles 5| to 54, and the angle Q being the angle through which the armature has rotated from the new brush position as mentioned above. Solving Equation 173 as before, then e=E sin 2(62-l-R) +C (174) Since e=0 when 62:0, as in the preceding case, the constant C in Equation 174 is equal to E sin2 R. Consequently, Equation 174 becomes,

e=E sin 2(Q-l-R) -E sin2 R (175) As in the preceding case, Equation 175 holds for Q=O to Qzi) degrees, and, for Q=180 degrees to Q=360 degrees, becomes,

Similarly, the equations for the voltage wave forms of the remaining pairs of adjacent brushes wi11 be identical to Equations 175 and 176, except that these voltage waves will be degrees out of phase with respect to each other as in the preceding case.

It will be apparent that a wide variety of wave forms may be obtained between any pair of adjacent brushes by varying the value of the angle R in Equations and 176. Considering the extreme case where the brushes ||6 and for example, are displaced to occupy the positions occupied by the brushes H5 and H6, as shown in Fig. 2, so that the angle R=90 degrees, Equation 175 becomes,

Equation 178 is obviously the equation for the voltage generated by the next pair of adjacent brushes, ||l| and H8, which lag the brushes ||6 and by 90 degrees.

Considering an intermediate case where R=45 degrees, Equation 175 becomes,

e=E sin2(Q-l-45)-`E sin2 45 (179) or e=E sin2(Q-}-45) -E/2 (180) Simplifying, Equation 180 becomes,

e=E sin 2Q/2 (181) As in the previous case, Equation 181 holds for Q=0 to Q=180 degrees, the equation for Q=180 degrees to 62:36() degrees being,

Equations 181 and 182 also apply to the voltages generated between the remaining pairs of adjacent brushes except that these voltages are 90 degrees out of phase with respect to each other as in the preceding case.

Referring to Fig. 9, the wave form represented by Equations 181 and 182 for the voltage gene'rated between the brushes |16 and is indicated by the dotted curve |35, the curve |85 including two positive pulsations |66 and |81, each of 90 degrees duration, then two negative pulsations 188 and |89, each of 90 degrees duration, then two more positive pulsations, only one of which, |96, is shown, etc. The voltage wave for the lagging pair of adjacent brushes, 'l and I8, is indicated by the dashed curve ISI which is identical to the dotted curve |85 except for a 90 degree'phase lag, the curve ISI including two nega-- tive pulsations |92 and |93, Itwo positivevpulsations |94 and |95, etc.

The sum ofthe twophases |85 and AISI may be obtained by connecting the brushes H6 and Ii, as indicated schematically by the dimensional error,1 it of Fig. 8, this sum being represented by the solid line E91 of Fig. 9. The curve |91 includes a positive pulsation v| 98of90 'degrees duration, a no voltageperi'od |89 :of S30-degrees duration, a negative pulsation-ZUU of 90 degrees duration, a no voltage band 20| of 90- deg-rees-duration, a positive pulsation 202 of. 90 degrees duration, etc.

By connectingfthe .brushes |'I5 and |11, asindicated schematically by-the dimensional arrow 2&3 of Fig. 8, as wellvas theH brushes yIHS and H8, a curve 204 which is identical to the curve |91 but which lags the'latter by' 90 degrees, may also be derived'as illustrated.inFig. l0. :The Acurves |91 and 204 combined are similar to either of the curves H55 and 19| .of Fig. 9foradjacentmpairs of adjacent brushes, except that the magnitude of the pulsations of this combination is-V doubled over that of the pulsations |86 to |90, or |92 to |85.

- Itwill be apparent :that by employing various brush circuits and yvarious values for the brush angle-R, a great. many wave forms -may be derived in addition'to .those illustrated in Figs. 4, 6, '1,' 9, and l0, thenumber of wave forms possiblelibeing limited only.y byit-he number of possible brush circuits and brushV angle combinations. Some oi these7 wave for-msfmay'beiuseful in. electrical therapy. Others are peculiarly' adapted to electric hammer operation. Consequently, I do not intend to be limited to the particular wave forms disclosed and the particular applications suggested, since a wide'varietyof wave forms may be derived, and many applications therefor other i than those mentioned will be apparent tocpersons skilledin the art.

One of the features of my machine whenxoperating as an alternator or as anind-uction generator, is that the voltage will build up to full load voltage substantially within one revolution. As is well known in the art,rconventional generators require many revolutions before the output voltage builds upfto full load.

The description of the operation of my electrodynarnie machine hasthusifar. been concerned with the operation yof the embodiment of Figs. l and 2 as an alternator which is 'capable of generating alternating current -when-.-t-he---fie1d windingsY 5| toV 54. are excited by a source-ot. direct current such as the Vbattery i6 I-,umy improved commutator structure being responsible for the wide variety of wave forms Aobtain-able at the brushes I5 and |8. As previouslystated, the machine is also capable of operating as. an induction generator to perform a variety of functions, the operation thereof as an induction. generator and the eiect of my improved commutator structure 'on the operation thereof as such being'the'subjects of the following paragraphs.

-Various brush circuits may be employed when the machine is operating as anindu'ction generator, one of these being shownin Fig. 1. The lines H9 and |2| from the brushes ||5 and` H1, respectively, are connected to theload |25, the brush I 1 being connected to a battery 2 0 by the line |2| and a line 2| I. lThe line |22 from the brush ||8 is connected to a double'throw switch 'N2 which is movable between two contacts 2|3 and 2|4, these contacts being connected to the 12 line 2M on' opposite sides ofv the battery 2|0. When the machine operates as an alternator, as previously discussed, the switch 2| 2 is in the neutral position shown so that the brush I8 is out of the circuit.

A load 6 may be connected to the lines 59 and Sii of the field circuit by lines 2|1 and 2|8, respectively, the line 211 having a switch 2 i9 therein to exclude the load from the field circuit when the machine is operating as an alternator as previously discussed. When the machine is operating as an induction generator, as will be described hereinafter, the switch Zit will be closed, and the switch 52 will be open to exclude the battery 6| from-the field circuit.

Considering the operation of the machine as an induction generator with the load |25 in the armature circuit and the load 2id in the field circuit as shown in Fig. 1, moving the switch 2|2 to the contact 2|@ will include the battery 2 I0 in the brush circuit, thereby introducing a direct current into the armature winding 61. As the armature E5 is rotated by any suitable driving means (notrshown), it vwill lbe apparent that the direct current from the battery 2li! will create a rotating magnetic field as it flows through the armature winding 61. The speedof this rotating fieldis equal to the rotational speedvof the armature 65, i. e., one cycle per revolution of `the armature.

Since the load 25S is inthe field circuit, an alternating current will be generated in the eld windings 55 to 58 as the lines of force in the rotating magnetic field are cut bythe conductors comprising the field windings. The frequency of the alternating current generated in the field circuit is, of course, equal to the rotational speed of the armature 65, i. e., one cycle per revolution of `the armature. Since the embodiment illustrated in Figs. 1 and 2 includes four poles, the synchronous speed of the armature 65 is equal to one-half of the frequency of the alternating current generated in the eld circuit, comparing the machine to a conventional induction motor.

` The alternating `current generated in the eld circuit produces another rotating eld in the eld windings `55'to 58, as inthe case of a conventional induction motor, so that the polarities of the field poles 5| to `51| are alternately'north and'south, instead of remaining either north or south as is the case when the eld windings are excited by 'direct current when the machine operated as an alternator. The frequency of the changing polarity of the poles 5| to 54 is determined bythe frequency of the alternating current generated in the eld circuit, which is in turn determined bythe speed of the armature 65, as previously discussed. Consequently, the changing' polarity of the poles 5| to 54 is so related to the speed of the armature 65 that a pulsating direct current is generated at the brushes H5 to H8, the frequency of these pulsations being determined by the armature speed. By employing various brush combinations, various wave forms may be derived, the particular brush circuit shown in Fig. 1 being adapted to provide at the load |25 a positive pulsationwhich is followed by a period of no activity, thence by another positive pulsation, another period of no activity, etc., all vas indicated by the curve 220 adjacent the load |25 in Fig. 1.

As previously mentioned., the output of the machine may be divided between the field circuit and the armature circuit in any proportions when operating as an induction generator. For example, if each of the eld windings 55 to 58 are shorted individually to provide, in effect, a squirrel cage construction, all of the output will be in the form of pulsating direct current in the brush circuit.

The function of the battery 2lll in the brush circuit illustrated in Fig. l is primarily to start the machine generating, the battery serving as a primer means. The machine will continue to operate inductively in the manner described if the switch 212 is moved to the neutral position illustrated. Ii the switch 2l2 is moved to the conn tact 2I3 to short circuit the brushes lll and llt, the machine will stop generating substantially instantaneously and will not start generating again until the switch 2&2 is again moved to the Contact 214 so that the priming operation described previously is repeated.

Since the battery 210 determines the direction of flow of the priming current through the armature winding 61, it will be apparent that if the battery is reversed, the current derived therefrom will merely flow in the opposite direction. The net result of this current reversal in so far as the battery 2l@ is concerned is that the direct current generated in the brush circuit will be reversed. Consequently, the direct current generated in the brush circuit will always charge the battery v2li). Since the direct current generated is pulsating, as indicated by the curve 22e in Fig. 1, the battery 2i0 within. the iirst one-half of the cycle discharges a relatively small amount of amperage to prime and start the unit to gen erate inductively in a quick pick up in both voltage and load substantially within one cycle oi its armature, and continuous generating shows no indication of any discharge from the battery 2 I0 through oscilloscope observation or meter indication, but is in reverse shows that the unit charges the battery 2I0 regardless to terminal connections. The charging rate varies propern tionally t the battery ilii voltage as shown in curves in Figs. 24, 25 and 26.

The battery Zlil is charged., and since the bat-- tery controls the direction of current iiow, 'the battery will be charged regardless of how its terminals are connected in the brush circuit. This feature of my invention is shown more clearly in Figs. 13 to 18, inclusive.

Referring particularly to Fig. 13, I show a brush circuit wherein the brushes llt and lli are short crcuited and are connected to the brush l Il through a battery 225. t A in Fig. 13, I show the directions of current ilow during the first one-half (180 degrees) of the operating cycle, and at B I show the directions during the second onen half of the cycle, the flow directions having been obtained with directional ammeters during tests of the machine. The pulsations of the generated direct current corresponding to the portions oi the operating cycle shown at A and B in Fig. 13 are shown at A and B in Fig. 15, respectively. Figs. 14 and 16 are identical to Figs. 13 and 15, respectively, except that the battery is reversed, the reversed directions of current ilow during the rst and second halves of the 0perating cycle being shown at C and D in Fig. lll, respectively, and the corresponding generated direct current pulsations being indicated at C and respectively, in Fig. 16. Thus, regardless of the manner in which the battery 225 is connected in the brush circuit, the battery is always charged by the generated direct current during one-half of the cycle to a greater extent than it is discharged during the other one-hallc of the cycle.

In Fig. 17, I show a brush circuit wherein the brushes Ill and H8 are short circuited and the brushes H5 and lili are also short circuited, the two pairs or shorted brushes being connected through a battery 226. At E and F in Fig. 17 are shown the directions of current liow during the first and second halves of the operating cycle, the battery 222 being charged when the directions of current flow are as shown at F. Fig. 18 is identical to Fig. 17 except that the battery 226 .is reversed in the brush circuit, the directions of current ilow during the rst and second halves of the cycle being shown at G and H, respectively. lt will be noted that reversing the battery reverses the directions of current flow throughout the brush circuit so that the battery is always charged by the pulsating direct curront generated in the armature 65 during onehalf of the operating cycle regardless of how the battery is connected. 'Various brush circuits other than those shown in Figs. 13, 14, 17, and 18 may be employed with similar results.

In Figs. 19 to 21 are shown other brush circuits which are similar to those shown in Figs. l'l and lil, the brushes H5 and H6 being short circuited and the brushes i Il and l |18 being short circuited. The shorted brushes lll and H8 in 19 to 2l. are connected to a switch 232 which is movable between contacts 23E and 232, the conu tact being connected to the shorted brushes ilb and liti by a line and the contact 232 being connected to the line 233 through a battery In addition to the battery 234, a variable rer tance 225 is connected in the circuit shown i9, and an inductance 235 is connected in the circuit shown in Fig. 21. The voltage supplied by the battery 234 regulates the voltage of the alternating current generated in the field windings 55 to 52, the resistance 235 and inductance vary the relationship between the battery voltage and field voltage as shown in 2li to 26, which correspond to the circuits shown in 19 to 2l., respectively.

The battery voltage Versus held voltage curves shown in Figs. 24 to 25 represent the results of tests conducted with a four-pole, one-quarter horsepower repulsion rnotor which was reworked to provide the embodiment shown in Figs. l and In obtaining these battery voltage versus eld voltage curves, all other variables were held constant except that the curves shown in Fig. 24 were obtained with the resistance 235 in the circuit, and the curve shown in Fig. 26 was obtained with the inductance in the circuit. Thus, Fig. 2/1 illustrates the eect of adding the resistance 235 to the circuit shown in Fig. 20, and 26 shows the effect or adding the inductance thereto. Referring to Fig. 25, it will be noted that without the inductance 236 or resistance 235 in the circuit, the alternating current voltage generated in the held windings 55 to increases uniformly, whereas with the resistance 235 in the circuit, as shown in Fig. 19, the eld voltage is substantially constant at 60 volts as shown in 24. Adding the inductance to the circuit of Fig. 20 as shown in Fig. 21, does not appreciably affect the relationship between battery voltage and field voltage as may seen by comparing 25 and 26. The efrect of the resistance 235 and inductance 236 on the direct current generated in the armature G5 to charge the battery 234i may be seen by comparing Figs. 24 to 26, which correspond to the circuits shown in Figs. 19 to 21, respectively. It

I should-be. noted.that the armature current values shown in Fig.-24 are -in milliamperes whereas the Values Ashownv in Figs. 25 and 26 are in amperes.

It will be understood that the test results shown in Figs. 24 to 26 are for the particular size machine employed, and that the results shown will be different for machines of other sizes. Consequently, it will be understood that the results shown are intended as illustrative only, and I do not intend to be limited thereto.

Figs. 22 and 23 illustrate additional brush circuits which may be employed in connection with my electrodynamic machine. In Fig. 22, the brushes i I6 and I8 are short circuited and may be connected to the brush |1 by a switch 246 which is movable between two contacts 24| and 262 to include in or exclude from the circuit a battery 2.43 and an inductance 244. In Fig. 23, the brushes -||6 and H3 are also short circuited, and the brush ||1 is connected to a switch 256 which is' movable between two contacts 25| and 252, the contact 25| being connected to the shortedr brushes ||6 and H8, and the contact 252 beingy connected to the brush ||5 through a battery 253 and a variable resistance 254. Various other brush circuits may also be employed, some being useful for certain applications, and others bein-g useful for other applications.

An important advantage in including the resistance 254 in the brush circuit shown in Fig. 23 is that the machine will not operate with no load in the field circuit, whereas the machine will operate with no load in the eld circuit if no resistance, or only a small resistance is employed.

In Figs. 11 and 12, I show another manner in which my .electrodynamic machine is capable of operating as an induction generator. The brushes ||5 and ||1 are connected to the load |25 as in Fig. 1, and the field windings 55 to 58 are connected to the battery 6|, also as in Fig. 1. In Figs. 1l and 12, however, the resistance 63 of Fig. 1 is variable, the resistance of the eld circuit being variable by means of a rotatable member 260. contacts 26| and 262 which are spaced so that when the member 269 disengages the contact 26| and engages the contact 262, the battery 6| is excluded from the eld circuit.

When the member 260 is in the position shown in Fig. 11, the resistance of the eld circuit is such that the machine operates as an alternator to generate a flat-top wave 263 which is the same as the at-top wave |66 shown in Fig. 6 and described previously. However, when the member 2.60 is rotated to the position shown in solid lines in Fig. 12, the resistance of the field circuit becomes such that the dampening effect of the battery 6| is reduced so that the machine may operate partially as an induction generator, thus generating pulsating direct current in the brush circuit as indicated by the curve 264. When moving the member 260 to the contact 262, as indicated in phantom in Fig. 12, so that the battery 6| is excluded from the field circuit and the dampening influence thereof eliminated, the machine operates completely as an induction generator to generate its maximum voltage as indicated by the curve 265 in broken lines. The gap between the contacts 26| and 262 must be such that the member 26|) may move from one to the other without opening the eld circuit, orthe machine would otherwise stop generating. Theoperation of my electrodynamic machine in this manner results from decreasing and/or The resistance .63 includes a pair of 16 eliminating the dampening effect of the battery 6| on the eld circuit so that the machine can operate as an induction generator.

In Figs. 27 and 29, I show embodiments of my invention which are similar to the embodiment shown in Figs. 1 and 2, and which are capable of performing similar functions. The embodiment shown in Fig. 27 includes eight poles 21!) having windings 21| thereon which are adapted to produce alternate north and south poles when excited by a source of direct current (not shown). The embodiment of Fig. 27 includes an armature winding 28|) having terminals 28| to 365, etc., and includes a commutator Sli] having segments 3|| to 328, the terminals 28| to 268 being connected to the segments 3H to 328, respectively. Brushes 33| to 334 engage the commutator 3|0, the brushes being spaced 90 degrees apart.

The segments of the commutator 3|[l are divided into four groups 335 to 338, each group being of a length such that it subtends an angle of degrees. The segments 3|! to 3|6 of the group 335, and the segments 326 to 325 of the group 331 are one-half the length of the segments 3I1 to 3|9 and 326 to 328 of the groups and 338, respectively.

Fig. 28 illustrates one of the wave forms which .may be derived when the embodiment of Fig. 27 is operating as an alternator, i. e., with the field windings 21| excited by direct current. Various other wave forms may also be derived as discussed previously, and this embodiment is also capable of operating as an induction generator in the manner discussed previously.

The embodiment shown in Fig. 29 includes four poles 349 having windings 34| thereon which are adapted to produce alternate north and south poles when connected to a source of direct current (not shown). This embodiment includes a eld winding 359 having terminals 35| to 315, etc., and includes a commutator 38] having segments 38| to 392, the terminals 35| to 362 being connected to the segments 38| to 392, respectively. Brushes 393 to 396 engage the commutator 389, the brushes being spaced 90 degrees apart.

The segments of the commutator 38D are divided into four groups 391 to 469, the groups 361 and 399 each subtending an angle of 45 degrees, and the groups 398 and 469 each subtending an angle of degrees. The segments 38| to 333 of the group 391, and the segments 381 to 389 of the group 399 are one-third the length of the segments 384 to 366 and 339 to 392 of the groups 398 and 400, respectively.

Fig. 30 illustrates one of the wave forms which may be derived when the embodiment of Fig. 29 is operating as an alternator, i. e., with the eld excited by direct current. The wave form shown is a 45 degree at-top wave with 135 degree reversal gradients. Various other wave forms may also be derived, and this embodiment may also be operated as an induction generator as previously described.

Thus, my invention provides an electrodynamic machine which may be employed either as an alternator or an induction generator. Since various embodiments of the machine other than those disclosed herein may be employed without departing from the spirit of the invention, and since the machine is susceptible to applications other than those mentioned herein, I do not intend to be limited to the specic disclosures contained herein, but desire to be afforded the 17 protection offered by the full scope of my appended claims.

claim as my invention: 1. In an electrodynamic machine of the character described, the combination of: relatively movable primary and secondary members; a winding on said primary member; an armature winding on said secondary member, said armature winding including a plurality of successive terminals; a commutator including a plurality of mutually insulated successive segments which are connected to the respective successive terminals of said armature winding, the length of one of said segments being substantially greater than the length of the remaining segments; and brushes engaging said commutator.

2. In an electrodynamic machine of the character described, the combination of: relatively movable primary and secondary members; a winding on said primary member; an armature winding on said secondary member, said armature winding including a plurality of successive terminals; a commutator including a plurality of successive mutually insulated segments which are connected to the respective successive terminals of said armature winding, said segments being arranged in groups of one or more successive segments, the length of said segments comprising one of said groups being substantially greater than the length o' said segments comprising another of said groups; and brushes engaging said commutator.

3. lin an el'ectrodynamic machine of the character described, the combination of a stator having a multipole field winding; a rotor having a winding which includes a plurality of terminals; a commutator carried by said rotor and includig a plurality oi segments which are arranged plurality of pairs of circumferentially ar- .paced 18o degrees apart, and said groups iother of said. pairs being spaced 180 degrees anat and being disposed between said groups of said one pair, said segments comprising said groups oi said. one pair being longer than said sa,m

' comprising said groups of said other pair;

-necting successive terminals of said rotor winding to successive segments of said groups; and brushes engaging said commutator.

fi. in an electrodynamic machine of the char*- described, the combination of a stator having a multipole eld winding; a rotor having a which includes a plurality of terminals; ciutat-or carried by said rotor and includof said rotor winding, said sego' arranged in a plurality of pairs of ferentially arranged groups, said groups e said pairs being spaced 18) degrees and said groups of another of said pairs g spaced 130 degrees apart and being dis- Y d between said groups of said one pair, said nt ising said groups of said one pair d cc ut-aten i eiectrodynamic machine as defined in herein said pairs of groups are two in and wherein the lengths of said segae such that each of said groups sub- Ade a.. angle of 90 degrees.

ciectrodynamic machine as dened in wherein said pairs of groups are two in g, wherein each of said groups of said one pan comprises a single segment of a length such yaged groups, said groups of one of said pairs movable primary and secondary members; .winding on said primary member forming a vmovable primary and 'secondary members;

18 that it subtends an angle of degrees, and wherein each of said groups of said other pair comprises a plurality of segments of a length such that each of said groups of said other subtends an angle of 90 degrees.

'7. An electrodynamic machine according to claim d including variable resistance means in series with said held winding.

8. in an electro-dynamic machine of the character described,I 'the combination of: relatively movable primary and secondary members; a winding on said primary member forming a series oi poles, successive poles being of opposite polarity; an armature winding on said secondary meinber, said armature winding including a plurality oi conductors arranged about the periphery or said secondary member, said conductors being connected in series, a' group of adjacent conductors extending over a substantial portion ci said periphery being provided with corresponding terminals; a commutator including a pluralm of circumferentially arranged segments, the lengths ci" some segments being substantially greater than the lengths of other segments; oonductor leads connecting successive terminais or the armature winding to successive commutator vsegments including some commutator segments or" greater length and some of lesser length; and brushes engaging said ccmmutator.

9. An electro-dynamic machine as deiined in claim e in which said portion is greater than about the angular spacing between successive poles and the ends of said group are separated by an angular distance greater than about the spacing between adjacent poles.

lo. in an electro-dynamic machine of the character described, the combination oi: relativel a series oi poles, successive poles being of opposite polarity; an armature winding on said secondary ber, said armature winding including a plurality of conductors arranged about the periphery oi said secondary member, said conductors being connected in series, a group of adjacent conductors extending over a portion of said periphery equal to more than about the spacing between successive poles being provided with correspond- Iing terminals; a commutator including a pleural-- ity of segments arranged in a pluraiity of circulnierentially arranged groups, the lengths oi the segments comprising one of said groups being substantially greater than the length oi the segments comprising another of said groups, successi-ve terminals of the armature winding being connected to successive commutator segments inoluding some commutator segments ci said one group .and some of said another group; and brushes engaging said commutator.

1l. An electro-dynamic machine as donned in claim l0 in which said groups of commutator segments extend over angular distances equal to at least about half the angular spacing between poles.

12. An electro-dynamic machine as defined in Iolairn l0 in which said groups of commutator segments extend over angular distances equal to at least about the angular spacing between poles.

13. In an electro-dynamic machine of the character described, the combination of: relatively a winding on said primary member forming a series Y of poles, successive poles being of opposite poiarity; an armature winding on said secondary member, .said armature winding including a plurality of conductors arranged about the periphery of said secondary member, said conductors being connected in series, a plurality of said conductors over a substantial portion of sai-d periphery being provided with corresponding terminals; a commutator including a plurality of circumferentially arranged segments, successive segments being connected to successive terminals, the angular spacing betweenfsome of the interconnected terminals and segments being substantially greater than the angular spacing between other interconnected terminals vand segments; and brushes engaging said commutator.

le. An .electro-dynamic machine as defined in claim in which the -di'erence between said angular spacings is at least equal to about half the angular spacing between successive poles of the primary member.

15. An electro-dynamic machine as defined in claim 10 in which the difference between said angular spacings is at least equal to about the angular spacing between successive poles of the primary member.

16. A multipolar electro-dynamic machine as described, comprising a stator wound with 2N alternate polarity elds (where N is any whole number not less than 2), a rotor provided with a uniformly distributed winding, a commutator provided with a plurality of .angularly spaced segments, said segments being divided into groups, successive segments of one of said groups being uniformly connected to successively separated points on said rotor winding of corresponding angular displacement, successive segments of a second one of said groups being uniformly conm nected to successively separated points on said placement and multiple phase cyne alternating current between pairs of said brushes at 90 degrees displacement.

17. A multipolar electro-dynamic machine described, comprising a stator having a plurality of alternate polarity elds, a rotor provided with a distributed winding, a commutator provided with a plurality of angularly displaced segments, said segments being divided into groups, successive segments of one of said groups being connected to successively separated points on said rotor winding, the successive segments of a second one of said groups being connected to successively connected points on said rotor Winding spaced a distance substantially equal to a pole arc from said rst named points, there being a group of successive points on said rotor winding unconnected to said commutator, a plurality of brushes for said commutator whereby said fields are adapted to be inductively excited by said rotor to cause generating alternating current in said iield winding when a pair of said brushes are short circuited and in circuit with a direct current battery priming source through a further intervening brush of said brush groups wherein said priming battery takes a self adjusting charge regardless of terminal connection of said brush circuit.

18. A multipolar electro-dynamic machine as described, comprising a stator having a plurality of alternate polarity elds, a rotor provided with a distributed winding, a commutator provided with a plurality of angularly displaced segments, said segments being divided into groups, successive segments of one of said groups being connected to successively separated points on said rotor winding, the successive segments of a second one of said groups being connected to successively connected points on said rotor winding spaced a distance substantially equal to a pole arc from said rst named points, there being a group of successive points on said rotor winding unconnected to said commutator, a plurality of brushes for said commutator whereby said elds are inductively excited by said rotor and to generate alterna-ting current in said eld winding and generating direct pulsating current through pairs of said brushes in load when primed through a further intervening brush of said brush groups in circuit with a storage battery and said loaded pair of brushes and further means to destroy inductive generating by short circuiting said control brushes through a switch that omits the said battery.

19. A multipolar electro-dynamic machine comprising: a stator having a plurality of alternate polarity iields; a rotor provided with a dism tributed winding; a commutator provided with a plurality of angularly displaced segments; said segments being divided into groups; successive segments of one of said groups being connected to successively separated points on said rotor winding; the successive segments of a second one of said groups being connected to successively connected points on said rotor winding spaced a distance substantially equal to a pole arc from said first named points; there being a group of successive points on said rotor winding unconnected to said commutator; a plurality of brushes for said commutator by which said fields are caused to be inductively excited by said rotor so as to generate an alternating current in said 'eld windings when a plurality of said brushes are short circuited; and a priming circuit including storage battery connected to a plurality of said brushes to enable a relatively weak current from said battery to cause the machine to generate.

20. A multipolar electro-dynamic machine comprising: a stator having a plurality of alternate polarity fields; a rotor provided with a distributed winding; a cominutator provided with a plurality of angularly spaced segments; said segments being divided into a predetermined number oi groups; successive segments of the first of said groups being connected to successively separated points on said rotor winding of correspondng angular displacement; the segments of asecond of said groups being successively connected to points on said rotor winding of different angular displacement than the segments of said iirst group; the segments of the third and fourth groups being connected to said rotor winding similarly to said rst and second groups at points of opposite polarity; a plurality of brushes for said commutator including a pair of shortcircuited brushes arranged a predetermined number oi degrees apart; a priming circuit including a storage battery and certain of said brushes; and means for stopping generating of current in 21 the machine by excluding said battery from the priming circuit.

21. A multipolar electro-dynamic machine comprising: a stator having a plurality of alternate polarity elds; a rotor provided with a distributed Winding; a commutator provided with a plurality of angularly spaced segments; said segments being divided into a plurality of groups; successive segments of the first of said groups being connected to successively separated points on said rotor winding of corresponding angular displacement; tne segments of a second of said'7 groups being successively connected to points on said rotor Winding of different angular displacement than the segments of said :drst group; the segments of third and fourth groups being connected to said rotor winding similarly to said rst and second groups at points of opposite polarity; a plurality of brushes for said commutator; a first pair of brushes shortcircuited at 180 degrees apart; a second pair of brushes arranged 180 degrees apart and at 90 degrees displacement from said shortcircuited brushes; a storage battery; said second pair of brushes being in circuit with said storage battery; a resistor in said circuit, whereby to produce alternating current in said stator and pulsating direct current in said circuit adapted to charge said battery regardless of the manner in which the 'terminals thereof are connected in the brush circuit; and means for stopping generating of current in said stator and rotor by shortcircuiting one brush of said second pair of brushes and excluding said battery from the circuit.

22. A multipolar electro-dynamic machine comprising: a stator wound with 2N alternate polarity elds (Where N is any whole number not less than 2); a rotor provided with a uniformly distributed winding; a commutator provided with a plurality of angularly spaced segments; said segments being divided into groups; successive segments of one of said groups being uniformly connected to successively separated points on said rotor winding of corresponding angular displacement; successive segments of a second one of said groups being uniformly connected to successively separated points on said rotor winding spaced a distance substantially equal to a pole arc from said first named points; successive segments of third and fourth groups being nonunformly connected to successively separated points on said rotor winding between said rst and second named groups; there being a group of successive points on said rotor winding corresponding to an arc of two poles unconnected to said commutator; collector brushes in contact With said commutator, by which said fields are caused to be inductively excited by said rotor so as to generate an alternating current in said field windings when a plurality of said brushes are short circuited; and a priming circuit including a source of direct current connected in the brush circuit to enable a relatively Weak current from said direct current source to cause inductive generating of the machine.

CLINTON H. HULBERT.

REFERENCES CITED The following referenlces are of record in the le of this patent:

UNITED STATES PATENTS Number Nam'e Date 390,439 Bradley Oct. 2, 1888 461,297 Van Depoele Oct. 13, 1891 1,115,352 Walker Oct. 27, 1914 1,491,108 Sethman Apr. 21, 1924 1,515,971 Sethman Nov. 18, 1924 1,583,809 Stoller May 11, 1926 2,117,019 Conrad May 10, 1938 

